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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef FUCHSIA_BASE_RESULT_RECEIVER_H_
#define FUCHSIA_BASE_RESULT_RECEIVER_H_
#include "base/bind.h"
#include "base/callback_helpers.h"
#include "base/optional.h"
namespace cr_fuchsia {
// Helper for capturing a "result" of an asynchronous operation that is passed
// via a Callback<ResultType>, for later retrieval. An optional Closure may also
// be configured, to be called when the result is captured.
//
// This is primarily useful for tests, which use a ResultReceiver<> configured
// with a RunLoop::QuitClosure() to pump a message-loop until an asynchronous
// operation has completed.
template <typename T>
class ResultReceiver {
public:
ResultReceiver() : on_result_received_() {}
explicit ResultReceiver(base::RepeatingClosure on_result_received)
: on_result_received_(std::move(on_result_received)) {}
~ResultReceiver() = default;
// Returns a OnceCallback which will receive and store a result value.
base::OnceCallback<void(T)> GetReceiveCallback() {
return base::BindOnce(&ResultReceiver<T>::ReceiveResult,
base::Unretained(this));
}
void ReceiveResult(T result) {
DCHECK(!result_.has_value());
result_ = std::move(result);
if (on_result_received_)
on_result_received_.Run();
}
bool has_value() const { return result_.has_value(); }
T& operator*() {
DCHECK(result_.has_value());
return *result_;
}
T* operator->() {
DCHECK(result_.has_value());
return &*result_;
}
private:
base::Optional<T> result_;
const base::RepeatingClosure on_result_received_;
DISALLOW_COPY_AND_ASSIGN(ResultReceiver<T>);
};
} // namespace cr_fuchsia
#endif // FUCHSIA_BASE_RESULT_RECEIVER_H_
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